Despite the use of effective antibiotics in combination with cardiopulmonary support, the mortality rate from sepsis and septic shock for the last three decades has remained high (29%. Furthermore, the incidence of sepsis and septic shock appear to be increasing. New therapeutic approaches with wide clinical applicability are needed to lower the high mortality rate of this syndrome. Excessive release of inflammatory mediators contributes directly to the pathogenesis of organ injury and death occurring during severe infection complicated by sepsis and septic shock. Nuclear factor kappa B (NF-KB) is a nuclear transcription regulatory protein central to the activation of several different genes encoding proteins associated with the inflammatory response during sepsis. Under normal conditions, NF-KB remains sequestered in an inactive state in the cytoplasm under the control of its cytoplasmic inhibitor (I-(B) proteins. However, differing kinds of stimuli including LPS (the toxic moiety of gram-negative bacteria) and cytokines (e.g. TNF alpha and interleukin-6) cause the phosphorylation, ubiquitinylation, and the subsequent degradation of I-KB proteins in turn resulting in the activation of NF-KB. Then the DNA-binding subunits of NF-KB migrate into the nucleus and activate expression of target genes that code for proteins in the inflammatory and immune responses, such as chemokines, cytokines, inducible nitric oxide synthase (iNOS), and adhesion molecules. Many of these gene products have been closely associated with the pathogenesis of the hemodynamic instability and organ injury occurring during sepsis and septic shock. Therefore, agents designed to inhibit NF-KB may have broad antiinflammmatory effects that could be beneficial during sepsis. However, many of the host mediators associated with the inflammatory response and under the control of NF-KB also contribute to innate immunity and the clearance of bacterial infection. Suppression of NF-KB during sepsis could therefore also worsen underlying infection. The present protocol tested the effects of of modulating NF-KB with parthenolide in a murine model of sepsis. Parthenolide is a sesquiterpene lactone derived from Asteraceae plants. Parthenolide has been reported to improve survival when administered up to 3 hours following intravenous LPS stimulation in mice or rats challenged with intraperitoneal or intravenous LPS respectively. However in the investigations that have thus far been completed in a fluid supported mouse model under this protocol, inhibition of NF-KB with parthenolide has been harmful with LPS challenge. These results emphasize the potential protective effect NF-KB has in host defense against microbial toxins. Work in this project is now centered on investigating tissue expression of NF-KB over the time following LPS challenge. Thus far, studies in the lung have shown that NF-KB expression is related to the dose of LPS challenge. Furthermore, parthenolide?s effects on NF-KB expression appear to be time dependent. Although levels are decreased early, they are increased late after LPS challenge with parthenolide. Similar changes with parthenolide were noted with plasma cytokine levels. Overall, these studies suggest that the effects of NF-KB inhibition in animal models of sepsis may be variable. Understanding the effects of inhibiting such a central mediator in the inflammatory and host responses during sepsis must be well defined before this is explored in patients.